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TITLE: DESIGN GUIDE FOR DRAG EMBEDMENT ANCHORS

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*• ITUAD- R- Taylor, NCEL and MU nun. p valent, Brian Watt & Associates

DATE: January- 1984

SPONSOR: Naval Sea Systems Command ^£. MAR 5 1984

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PROGRAM NO: 42-040

NAVAL CIVIL ENGINEERING LABORATORY PORT HUENEME, CALIFORNIA 93043

5 MAR 384 This publication is required <■■■■■■■* fur administrative or operational fmm only. Distribution is limited to U.S. Government agencies. Ouier requests must be referred to the Naval Civil Knguieciing Laboratory. Port Hucnemc, CA 9J04J.

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Unclassified SECURITY CLASSIFICATION OF TMIS PAGE 'When Pmtm Fntned)

REPORT DOCUMENTATION PAGE 1 REPORT NUMBFR

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4. TITLE f-nd Submit) IffTlgV.a

DESIGN GUIDE FOR DRAG EMBEDMENT ANCHORS

7 AUTHORC»,

R. Taylor, NCEL and P. Valent, Brian Watt & Associates

9 PERFORMING ORGANIZATION NAME AND ADDRESS

NAVAL CIVIL ENGINEERING LABORATORY Port Hueneme, California 93043

t CONTROLLING OFFICE NAME ANO ADORESS

Naval Sea Systems Command Washington, DC 20362

14 MONITORING AGENCY NAME » AOORESSdf Ji«rr»nl (mm Conlr.>//m« Othrr)

READ INSTRUCTIONS BEFORE COMPLETING FORM

3 RECIPIENT'S C*T*LOG NUMBER

<7C) U 4 TYPE Of REPORT & PERIOD COVERED

Final; Sep 1982 - Sep 1983

6 PERFORMING ORG REPORT NUMBER

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to PROGRAM ELEMENT PROJECT TASK AREA A WORK UNIT NUM9ERS

62543N; 42-040

12 REPORT DATE

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»• SUPPLEMENTARY NOTES

H «EY »0»OSi nd pJfnM. 6v blor» mtmbr

Anchors, moorings, holding capacity, seafloor soils

-.* .IT! -«.»us a. J* It I mry wiJ iitrnnty ft» b!>,- * ni.mter<

This design guide provides an overview to the selection and sizing of drag embedment anchors and mooring chains and to the diagnosis and solution of typical drag anchor per- formance problems. The site information required for anchor type selection is outlined. Two options for sizing the drag anchor arc offered. The more exacting of these options includes a method for determining the moo'Hg load resistance developed by that length of mooring chain embedded in and sliding on ccücsivc seafloor soils. Example problems for anchor

continued

00 , j»N I) H?3 EOlTiONOf ' NOV »S IS OBSOLET» Unclassified SECURITY CL ASSlFlC AT,ON OF THI: PAOf ■ W>**l> /'*!• »-

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Unclassified SECURITY CLASSIFICATION OF THIS PAGEOU««! £>«<• Enimrmd)

20. Continued

system design on cohesionless and cohesive seafloors are provided. The last section outlines drag anchor performance problems and provides possible solutions. More detailed information can be found in the references.

D

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'Av.'t '■ i -no / -■<

0, Library Card

Naval Civil Engineering Laboratory DESIGN GUIDE FOR DRAG EMBEDMENT ANCHORS (Final), by R. Taylor. NCEL and P. Valent. Brian Watt & Associates TN-1688 71 pp illut January 1984 Unclassified

1. Anchors 2. Holding capacity 42040

This design guide provides an overview to the selection and sizing of drag emlicdment anchors and mooring chains and to the diagnosis and solution of typical drag anchor performance problems. The site information required for anchor type selection is outlined. Two options for sizing the drag anchor are offered. The more exacting of tiiesc options includes a method for determining the mooring load resistance developed by that length of mooring chain embedded in and sliding on cohesive seafloor soils. Example problems for anchor system design on cohesionless and cohesive seafloors are provided. The last section outlines drag anchor performance problems and provides possible solutions. More detailed information can be found in the references.

Unclassified SCCUS'TY Cl.ASStriCA*lOWOF T«liP4i|'«,n[',

•v" •

PREFACE

m The Naval Civil Engineering Laboratory (NCEL) was tasked to improve

the Navy's capability to select and design drag embedment anchors.

Beginning in 1979, NCEL has conducted a 3-year anchor test program,

sponsored by the Naval Facilities Engineering Command (NAVFAC) and Naval

Sea Systems Command (NAVSEA), to accurately describe drag embedment

anchor behavior. Data from this test program were used to develop and

validate procedures to predict anchor holding capacity as a function of

seafloor type and engineering properties.

Preparation of this design guide was sponsored by NAVSEA. The

guide is structured to be used by the novice as well as those experienced

in ocean operations or mooring design.

This design guide provides an overview to the selection and sizing

of drag embedment anchors and mooring chains and to the diagnosis and

solution of typical drag anchor performance problems. The site information

required for anchor type selection is outlined. Two options for sizing

the drag anchor are offered. The more exacting of these options includes

a method for determining ^he mooring load resistance developed by that

length of mooring chain embedded in and sliding on cohesive seafloor

soils. Tables or charts within this guide can be used independently for

routine anchor selection and cost estimating purposes, and they can be

used within the structured (flow-charted) format provided to determine

detailed anchor system performance. Depending on the design option

selected, this includes anchor drag distance, embedment depth, holding

capacity, anchor chain capacity, and characteristics of the mooring

chain system. Example problems for anchor system design on cohesionless

and cohesive seafloors are provided. The last section outlines drag

anchor performance problems and provides possible solutions. More

detailed information can be found in the references.

> |w.-.'.v.--V.^

,S ••,>•.-• •••-•--*■•• ■ri - ■' ^

,V1

CONTENTS

Page

1. ANCHOR SELECTION 1

2. DETERMINATION OF SEAFLOOR CHARACTERISTICS 4

A. Site Data Required for Drag Anchors 4 B. Soil Sampling Methods 5 C. Determination of Seafloor Material Type 5

3. SELECTION OF DRAG ANCHOR TYPE 11

4. SIZING THE ANCHOR 14

5. FACTORS OF SAFETY REQUIRED 15

6. OPTION 1 - HOLDING CAPACITY CURVE OPTION 16

7. OPTION 2 - ANALYTIC MODEL 29

A. Range of Validity of Option 2 29 B. Procedure 30 C. Modifications for Wire Rope and Oversized Chain .... 35

8. ADDED HOLDING CAPACITY FROM SLIDING CHAIN 45

A. Application 45 B. Procedure 45

9. IMPROVING ANCHOR PERFORMANCE 48

10. EXAMPLE PROBLEMS 52

A. Example Design for Sand 52 B. Example Design for Soft Clay 55

11. REFERENCES 66

12. LIST OF SYMBOLS 67

VI 1

vV •-■•-•- t v. ■•.

ANCHOR SELECTION

Fljke

DRAG ANCHOR ELEMENTS

Use Tables 1.1 and 1.2 to assess the suitability of the drag

embedment anchor for your application.

If the drag anchor is a good choice ...

or

If knowledge of the site is insufficient to make a choice ...

Go to Section 2.

If the drag anchor is a poor choice ...

Select and design an alternative anchor type.

See: Handbook of Marine Geotechnology, Chapters 1, 4, 5, and 6 Naval Civil Engineering Laboratory Port Hueneme, CA 93043 (Ref 1)

or

NAVFAC Design Manual DM-26: Harbor and Coastal Facilities Naval Facilities Engineering Command Washington, DC 20390 (Ref 2)

Table 1.1. Generalized Features of Drag Embedment Anchor Systems

Positive Features

1. Broad range of anchor types and sizes available.

2. High capacity (greater than 1,000,000 lb) achievable.

3. Standard off-the-shelf equipment.

4. Broad use experience.

5. Can provide continuous resistance even though maximum

capacity has been exceeded.

6. Anchor is recoverable.

Negative Features

7. Anchor functions poorly in rock/coral seafloors.

8. Anchor behavior is erratic in layered seafloors.

9. Low resistance to uplift loads; therefore, large line

scopes required to cause near horizontal loading at

seafloor.

10. Penetrating/dragging anchor can damage pipelines,

cables, etc.

11. Loading, for most anchor types and applications, must

be uni-directional.

Table 1.2. Performance of Anchor Types as Function of Seafloor Type and Loading Condition

Parameter

Anchor Type

Drag Embedment

Deadweight Pile Direct

Embedment

Seafloor Material Type Soft clay, mud + + - +

Soft clay layer (0 to 20 ft thick) over hard layer - + + 0

Stiff clay + + + + Sand + + + +

Hard glacial till - + + +

Boulders 0 + 0 0 Soft rock or coral 0 + + + Hard, monolithic rock 0 + - -

Seafloor Topography Moderate slopes, <10 deg + + + +

Steep slopes, >10 deg 0 0 + +

Loading Direction Omni-directional 0 + + -

Uni-directional + + + + Large uplift component 0 + + +

Lateral Load Range To 100,000 lb + + - +

100,000 to 1,000,000 lb + - + -

Over 1,000,000 lb 0 0 + 0

See Reference 1 for further detail

KEY: functions well normally not e good choice does not function

2. DETERMINATION OF SEAFLOOR CHARACTERISTICS

A. SITE DATA REQUIRED FOR DRAG ANCHORS

Topogr~

Slope of seafloor

Relief (greater than 1 meter (3 feet))

sand waves

slump features

Sedim~nt Layer Thickness

Investigate to 3 to 5 meters in sand and 10 to 15 meters in

clay

thickness of strata

- depth to competent rock

Seafloor Material Type

Classify by:

university and government contacts and literature (Table 2.1)

sampling

visual observations and testing

4

. .

B. SOIL SAMPLING METHODS

Obtain one sample from each anchor location.

For Sands and Gravel: Use grab samples and dredges (Figure 2.1)

For Clays, Silts and Muds: Use gravity corer (Table 2.2)

C. DETERMINATION OF SEAFLOOR MATERIAL TYPE

SOILS -- Can be deformed by finger pressure.

Differentiate between:

H SANDS (cohesionless) -- free draining

CLAYS (cohesive) -- slow draining

SANDS: More than 88% of material is composed of grains

visible to the eye (larger than No. 200 sieve,

0.074 mm in diameter).

Soil is nonplastic; segregates readily into

individual grains.

Gravity corers are often recovered empty

because sample is washed out during retrieval;

if empty, check corer cutting edge for evidence

of damage from gravel or rock. Use grab

sampler to verify sand.

.vv> ■->■•.:.

MUDS, CLAYS: Less than 88% of material is composed of grains

visible to the eye (larger than No. 200 sieve).

Soil is plastic, cohesive; worKs like a putty

or modeling clay.

CORAL Identified by rock dredge sample.

ROCK Identified by rock dredge sample.

For most moorings, further delineation of seafloor type is needed.

This is accomplished by determination of seafloor engineering properties,

Table 2.3 provides a more detailed breakdown and relates soil type to

generalized anchor performance.

■*-'-

fl

Table 2.1. Sources of Marine Geological and Geotechnical Data

Universities and Government Organizations

Lamont-Doherty Geological Observatory of Columbia University, Palisades, NY 10964

National Geophysical and Solar-Terrestrial Data Center, Environmental Data Service,,NOAA, Boulder, CO 80302

Chief of Operations Division, National Ocean Survey, NOAA, 1801 Fairview Avenue, Ease Seattle, WA 90102

Chief of Operations Division, National Ocean Survey, NOAA, 1439 W. York Street, Norfolk, VA 23510

Naval Oceanographic Office, Code 3100, National Space Technology Laboratories, NSTL Station, MI 39522

Scripps Institution of Oceanography, La Jolla, CA 92093

Chief Atlantic Branch of Karine Geology, USGS, Bldg 13, Quissett Campus, Woods Hole, MA

Chief Pacific Arctic Branch of Marine Geology, USGS, 345 Middlefield Road, Menlo Park, CA 94025

Woods Hole Oceanographic Institution, Woods Hole, MA

Journals and Conference Proceedings

Journals of Geotechnical Engineering, ASCE

Marine Geotechnology, Pergamon Press, NY

Canadian Geotechnical Journal, National Research Council of Canada, C;tawa, Canada

Geotechnique, The Institution of Civil Engineers, London

Ocean Engineering, Pergamon Press, NY

Offshore Technology Conference, Houston, TX (yearly)

Civil Engineering in the Oceans (1 through 4)

IS

Clomihell Snopptr

Figure 2.1 Grab samplers and dredges.

Table 2.2. Summary of Short Corer Characteristics

Chirtitrmtiit

r"

Value

Corff Ov*r«J! l.tn

m 0 98 lo 4 57

luiuail* 1 8))

h 2 5 to 15

lutu&lty 6i

»rifhi

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ll

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(UMisllv I 2 to 1 Bi

1 to IU

lutuAiU 4 to 6)

S«mpir l>.*fTifici

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lutudilt 64i

Sh.p Kfiju.fernen - »inch A of I truric

»ir i tpjbi ,ll Hippi-riing ifitr wofff *nj * rr

nui wilh tr. j..ffMit.ir (4v^'f ol wtctV

trinn * : n m r«. 12 ' rnm I n .n to 1 : m )

JfpenJ n, Uli Ulf Wf Of tflC i'OffT

\..t,.o( c, l»:r. : 'ir1 ■> vp*r* ..ore viuhTr\ \pttt v,>re

. UIlCI^ tn I . ap\ fnuif

- - - - * - * - * - * a i ■ - * - ~ ' .v.

•y Table 2.3. Influence of Soil Type on Anchor Performance

är

I v.

i

►V

1

1

Soil Type Description Remarks

Sand Medium to dense sanu with bulk wet Holding capacity is consistent

density (y ) of 110 to 140 pcf. b

Typical of most nearshore deposits.

provided sand fluke angle is

used.

Standard penetration resistance

(SPT) range - 25 to 50 blows/ft.

Mud Normally consolidated, very soft Holding capacity is reasonably

to soft, silt to clay size sedi- consistent provided anchor flukes

ment typical of harbors and bays. trip open.

Soil strength increases linearly Certain anchors (see Table 3.1)

with depth at 10 psf/ft ± 3 psf/ft. require special care during

Approximately equates to SPT of installation to ensure fluke

2 blows/ft at 20-ft depth. tripping.

Clay Medium to stiff cohesive soil. Good holding capacity which

Soil shear strength (s ) con-

sidered constant with depth.

will range between that pro-

vided for sand and mud. Use

mud value conservatively or

s range -- 3-1/2 to 14 psi. u

linearly interpolate between

sand and mud anchor capacity

SPT range -- 4 to 16 blows/ft. (stiff clay (14-psi) capacity

equals sand capacity).

For stiff clay (s > 7 psi) use

sand fluke angle

Hard Soil Very stiff and hard clay Holding capacity is consistent

(s > 14 psi, SPT > 16) and provided anchor penetrates. May

very dense sand (SPT > 50, have to fix flukes open at sand

Y > 140 pcf). b

fluke angle to enhance embedment.

Jetting may be required.

Seafloor type can occur in high

current, glaciated, dredged Use holding capacity equal to 75%

areas. sand anchor capacity.

Layered Heterogeneous seafloor of sand, Anchor pelformance can be

Seat" loor gravel, clay, and/or mud layers erratic. Proof-loading

or mixtures. desired to verify safe

I capacity.

« Continued

»Al

Table 2.3 Continued

Soil Type Description Remarks

Coral/Rock Can also include areas where Unsatisfactory seafloor for

coral or rock is overlain by a permanent moorings.

thin sediment layer that is

insufficient to develop anchor Can be suitable for temporary

capacity. anchoring if anchor snags on an

outcrop or falls into a crevice.

Consider propellant-embedded

anchors.

■ t>\

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1 » • .

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10

. -.% /• >. •.»•>,*.^v:

?. 3. SELECTION OF DRAG ANCHOR TYPE

Given the soil type, an anchor is selected based on:

(1) performance (see Tables 3.1 and 3.2)

(2) handling (see footnote a, Table 3.1)

(3) availability and cost

11

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Table 3.1. Relative Holding Capacity Performance of Several Anchor Types

• •>

Seafloor Consistency

Performance

Excellent Good Satisfactory

Soft (mud, Stevmud Stevdig Bruce Cast Stockless clay) Stato Stevin

Boss Flipper Delta Danfortha

G.S.* LWTa

Two-Fluke Balanced Hook

Stevfixa

Bruce Twin Shank Moorfast Offdrill II

Hard (sand, Stevdig Danforth Stockless hard clay) Stevfix G.S.

Bruce Twin Shank LWT Stato Moorfast Boss Offdrill II

Bruce Cast Hook Two-Fluke Balanced

For fixed/fully opened flukes on soft seafloors. Movable flukes may not trip.

12

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Table 3.2. Efficiencies of 15-Kip Drag Anchors in Cohesionless and Soft Cohesive Soils

K>v

Anchor Type

Efficiency

Cohesionless Soft Cohesive (Sand) Mud

Stockless 48-deg fluke angle

with movable flukes 4 2.2 with fixed flukes 4 4.3

35-deg fluke angle with movable flukes 6 -

with fixed flukes 6 -

Two-Fluke Balanced with ball guide 7 2.2

Danforth 11 8 G.S. 11 8, LWT 11 8a

Stato ^3h

9b

20 Moorfast 8 Offdrill II 8, Stevin - nl Stevfix 26 17a

Flipper Delta - 9fl Stevdig 26 lla

Stevmud - 22 Boss 23 20 Hook 7 17 Bruce Cast 23 3 Bruce Twin Shank 24 14

"»<

.For fixed fully opened flukes. For 28 deg fluke angle.

Holding Capacity (L.) = Efficiency (e) • Anchor Air Weight (W.)

(NOTE: These are ultimate holding capacities. Do not use for anchor weights over 15 kips.) Values are conservative for anchor weights less than 15 kips.

13

> -*•- ^^ML - JS.^ *_."/• *' .*._***J

V

4. SIZING THE ANCHOR

After selecting an anchor type, then size the anchor according to

one of the following options:

OPTION 1 -- HOLDING CAPACITY CURVE OPTION (Refer to Section 6)

Advantages: suitable for most Navy mooring applications including

permanent fleet moorings

valid for anchor air weights up to 50 kips

Limitations: assumes chain for mooring line with a factor of

safety (FS) of 3 on break strength

valid only when anchor can penetrate to full depth

OPTION 2 -- ANALYTIC MODEL - APPLICABLE ONLY TO MUDS AND CLAYS (refer

to Section 7). Option 2 is more complex than Option 1

and should only be used when Option 1 is limited.

Advantages: treats anchor and mooring chain independently

can be used where anchor drag is restricted

can be used where soil layer thickness is not

sufficient to permit full penetration of the anchor

valid for anchor air weights greater than 50 kips

most accurate method for deeply embedded anchor-chain

systems

Limitations: applicable only to muds and clays

14

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5. FACTORS OF SAFETY REQUIRED

The following are the factors of safety required* for the specified

mooring types:

Mooring Type Item Factor of Safety

For Navy fleet Stockless anchors 1.5 moorings:

High efficiency3 2.0 anchors

Chain in mooring 3.0 line

For other than Navy All anchors 2.0 fleet moorings:

Chain in mooring 3.0 line

High efficiency anchors are any of the group of large-fluked anchors similar to the Danforth, Moorfast, Stato, Stevin, Flipper Delta, or Bruce anchors commonly used to moor float- ing drilling units, as opposed to the Stockless-type anchors usually employed as conventional ship anchors.

*From NAVFAC Design Manual DM-26 (Ref 3),

15

^^^>C^^^O:^A:^. . .^fe^v^ yyj v.vv.

m

6. OPTION 1 - HOLDING CAPACITY CURVE OPTION

PROCEDURE

DEFINE LOADS AND SOIL TYPE

1. Determine required ultimate horizontal holding capacity.

a. Determine maximum design horizontal load, Hn - see NAVFAC

DM-26 (Ref 2) or other.

b. Determine required factor of safety, FS (Section 5).

c. Calculate required ultimate horizontal holding capacity,

Hy,

H„ = FS • Hr

2. Identify seafloor material type and characteristics (Section 2),

SELECT ANCHOR TYPE AND SIZE

3. Select anchor type (Tables 3.1 and 3.2).

4. Select anchor weight and calculate anchor-chain system ultimate

horizontal capacity, L.:

a. Select anchor air weight, W., for first trial from Figure

6.1 (sand/hard seafloors) or Figure 6.2 (soft). Use

TM = H|. to determine W.. Note required reductions in

holding capacity for anchors used in hard soil

(Figure 6.1).

16

LN^-'•->-•-••■'•••• ■-■ '-•-•-'

NOTE: POSSIBLE TO SKIP TO STEP 6 FOR MOST ROUTINE*

ANCHOR-CHAIN MOORINGS

Determine TM for the selected anchor from Figure 6.1

(sand/hard seafloors) or Figure 6.2 (soft).

5. Check adequacy of drag distance,

a. Adjustments to L.:

(1) When drag distance in mud is limited, the anchor may

not penetrate deep enough to mobilize its full

capacity. Compare allowable drag distance (D) to

maximum required to achieve ultimate capacity. If D/L

MAX. (Figure 6.3) • L > drag distance allowed, then

determine the percentage of TM mobilized, r, as a

function of normalized drag distance from Figure 6.3

for mud. See Figure 6.4 or refer to manufacturer's

literature for fluke lengths (L).

(2) In sand, mobilization of ultimate anchor capacity

requires 10 fluke lengths drag for movable flukes and

8 fluke lengths for fixed flukes. One or two fluke

lengths may be required for tripping in soft soils.

Hard soil drag distance is usually not critical. Drag

distance (after fluke tripping) is about 2-1/2 fluke

lengths to ultimate capacity and 1 fluke length to

safe capacity (1/2 ultimate).

*Refers to noncritical moorings where anchor dragging is not cata-

strophic, where seafloor characteristics are generally well known,

and where historical anchor data are available.

17

b. Check adequacy of selection.

(1) If TM differs significantly from required capacity (H

or Hpj depending on requirement), then repeat step 4

with new anchor size and/or type selection.

U

(2) Determine safe anchor mudline capacity:

tv

TMS = VFS

If !„<. < L. at a specified design drag distance, use

L. = TMC. and compare to the maximum design horizontal

load Hp.. If TM < Hp., select a larger anchor.

6. Check adequacy of soil thickness.

a. Obtain anchor fluke tip penetration, d., required to

develop full capacity (Table 6.1).

b. If soil thickness, t, is less than anchor penetration

required, d., then:

(1) Select new anchor requiring less penetration, or

(2) Go to Option 3 for mud seafloor.

DETERMINE CHAIN SIZE AND LENGTH

7. Select chain size.

a. Estimate chain required breaking load, T IT

T|j = 1.15 • FS • Hp. (FS -- 3 recommended for chain)

18

•-* v" «_' *-" V V •--"v'•>!-"■> .'^ .v-,% v.-^vV V."V>\Ilv^

b. Select chain size, D (Table 6.2),

c. Calculate chain maximum design tension at top of catenary,

Tp. (Figure 6.5).

d. Calculate required chain breaking load, T,,:

TU = FS * TD (FS = 3 for chain)

e. Check adequacy of chain size.

(1) If T|| differs significantly from chain breaking load

(Table 6.2), then repeat steps b through e with new

selection.

(2) Chain breaking load should be at least 1.5 • maximum

anchor-chain system capacity, L..

8. Determine chain length required.

a. Calculate catenary length, s (Figure 6.5).

b. Calculate total chain length required, Lf:

(1) Sand/hard seafloor:

4 " s

(2) Soft seafloor (mud)

L. = s + H(J \ and s in feet, H.. in kips)

19

«\<\-.

9. Determine anchor setting distance to design load.

>i> a. Sand - Assume three fluke lengths drag distance needed to

achieve anchor design (safe) capacity for FS = 2

b. Mud - Calculate anchor setting distance D . Select D/L P

from Figure 6.3 at appropriate FS. FS = 2 recommended:

Dp = L(D/L)

v A flow chart of this Option 1 procedure is provided as

Figure 6.6.

&

2Ü

••>••••••---• ii «; i i ■ - - ' ■■---.

Table 6.1. Estimated Maximum Fluke Tip Penetration (d, ) of Some Drag Anchor Types in Sands and Soft111

Clayey Silts (Mud)

Anchor Type

Normalized Fluke Tip Penetration, (d. /L)

(fluke lengths')1

Sands/Stiff Clays Mud (e.g., Soft Silts and Clays)

Stockless3

Moorfast Offdrill II

Stato S'evfixa

Flipper Delta Boss Danforth LWTa

G.S. (type 2)

Bruce Twin Shank Stevmud

Hook

1

i

1

1

1

3

4

4-1/2

5-1/2

6

In mud, anchor flukes fixed fully open or held open initially.

Fluke tip penetration, dt = d./L • L; L from Figure 6.4.

21

•-:.».-*•. s* v* -." 1.' «." V %* V •-' ••'„*•. • - ."- ,N .*» »V.> «v. '•."-.••"».•.•.•-• . v • L* *->«."• -«- '-" -~' ,.-..% -V.'»k.N

i'- •

Table 6.2. Stud-Link Chain Proof and Breaking Loads

for Range of Chain Diameters

V" »■

f/f

tf»J

Diameter

Proof load B'eakmq toad Approx weiqht

Grade 2 Grade 3 Oil Rig Quality ORQ

Grade 2 Grade 3 Oil Rig

Quality ORQ

15

Fathoms

1000

Feet

1nches lbs lbs lbs lbs lbs lbs lbs lbs

IV 1"/,.

I1',

153000

166500 176000

214000

229000 247000

216000 232500 249000

214000 229000 247000

306000

327000 352000

325000 352500 380000

2353 2529 2/20

26144

28100 30222

1",,.. IV.

1' /,..

188500

201000

214000

264000

281000 299000

267000 285000 303500

264000

281000 299000

318000

337000 357000

37 7000 402000 427000

406000 432000 460000

2926 3'33 3336

32511 34811 37066

2 2'/,.

2'.

227000 241000 255000

318000

337000 357000

322000 342000 362000

454000 482000 510000

488000 518000 548000

3528

3/48 3971

39200 41644

44122

2'/,.

TU 2 /,..

289000 284000 299000

377000

396000 418000

382500 403000 425000

377000 396000 418000

538000 670000 598000

579100 610000 642500

4218 4454

4749

46866 49488 52766

2 V.

2',.

21'-

314000 330000 346000

440000 462000 484000

447000 469500 492000

440000 462000 484000

628000

660000 692000

6/5000 709500 744000

5016 5285

5580

55733 58722

62000

2";,..

2'<-

2'V

363000 379000

396000

b07000

b30000 554000

516000 640000 563000

507000 530000 554000

578000 603000

628000

726000

758000 792000

7 78500 813000

849000

5878 61/6 6471

66311 68622

71900

2". 2' Vii.

413000 431000 449000

578000 603000

628000

590000 615000 640000

826000 861000

897000

885000

026000 965000

6782 7111

7435

75355

79011

82611

21'/,.

3 3' ...

46 7000 485000 504000

654000 679000 705000

666500 693000 720500

748000 7 76050

804100

654000

679000 705000

732000 7b9OO0

787000

934000 970000 1008000

1046000 1084000

1124000

1005000 1045000 1086500

7777

8116

8460

86411

901/7 94000

3'/.

3V„ 3'/,

523000 542000 562000

732000 759000 787000

1128000

1169000 1210000

8815 9188

9543

9/944

02088

06033

3'',. 3 V.

3/,.

I'/i 3 V 3 '.

582000 602000 622000

643000 664000 685000

814000 843000

871000

900000 929000 958000

10)9000 1080000

1111000

II43OO0 1207000

1272000

_1338000 1405000 1474000

1543000 1613000 1686000

1757000

1903000

2062000 2128000

2280000 236/000 2612000

833150 862200 892100

922000 970000 1021000

"l120000 1206000 1252000

1298000 1347400 1397000

1569700 1672000 17 75000

1870000 1904000 1940000

2000000 2060000

2126000

2I9OOC0 2260000 23IOOOO

2444000

8I400D 8430. ■.". 871000

900000 929000 958000

1163000 1204000 1244000

1263000

1296000 1339650

9929 10314

10700

10322 114600 118888

1285000

132/000 1369000

1383100 1477000 1566000

1750000 1863400

193000g

1996500 2062600 2134000

2398000 2508000 26/6000

2805000

2852000 2900000

2995000

3090000 3185000

3280000

33490«) 3418000

3568000

11102 11488 11878

123355 12/644 1319/8

3 V,

3;. 3"-,.

728000

7 72000 794000

1019000 1080000 1111000

1143000 1207000 1272000

1338000 1405000 14 74000

1543000 1613000 1685000

1757000

1903000

2062000

2128000

2280001)

2J6/000 2512000

1455000 1543000 1587000

1632000

1724000 1817000

1911000 20C3000

2105000

2204 000

2305000 2407000

2509000

2718000

2932000 3039000

326/000 336/000 3589000

12661

13446 14097

14324

15272 16405

1406/8 149400 156633

169156 169689 1822/7

4

4". 4".

816000 862000 908000

956000 1004000 10b 3000

1102000 1153000 1203000

1255000

1359000

1466000

1520000

1629000 1684000 1 795000

4',. 4'-.

4 .

4''. 4 . b

5 . 5 . b .

V ' 5 . b ,

6 (i .

6'.

17441 1847/

19260

193/88 205300 214000

20263 21642

22/66

23902 26100 263/1

27500-

28/00 30054

32567 33600 36550

225144

240465 262955

'656/7

2'8888 2i30ll

306 ib5~ 3181.89 333933

361856

3/3333 4061 1 1

f :■•; i» ■ - ■

fcf.

KM

-' -»-!■»n»-'--.•■»

22

*■*■*-• '-*--•- »*- *'* i»ill .'.■_,...«- ■_ .--

Dense cohesionless soils (sands, gravels)

T„ is the ultimate capacity - Apply factor of safety

to determine operating load 1000

800

600

400

_ 200

U bo .8 T3 O X

o X!

100

5 6 7 8 9 10

Anchor Air Weight, W (KIPS)

Figure 6.1. Holding capacity at mudlinc - sand (anchor-chain system).

23

ll_filLllII_l_LXlJ-lJ I ' ->-.-.-. -. i v.-.'.i v." ■'^■'--^- '- fc*

Soft cohesive soils (soft muds) TV. is the ultimate capacity - apply factor of safety

to determine operating load 800

•o o X E

HI

C <

4 5 6 7 8 9 10

Anchor Air Weight, WA (KIPS)

20 30 40

Figure 6.2. Holding capacity at mudlinc - mud (anchor-chain system).

;£££^^ ••. -. < '»•..■". •.-,>"-"^-VN «\-"'.*' ^^^^^j^^^jj^^j^^, -^.1- .v.' ^^•^•v^.- vÄv^xvv.'.v.v.i. ■ .>". •■ :^

100

Drag Diftance/Flukc Length • • (DA.)

** ANCHOR FLUKE LENGTH AS DEFINED HERE WAS TAKEN FROM MANUFACTURERS' LITERATURE; MANUFACTURERS OFTEN INCLUDE THE CROWN AND TRIPPING PALM IN THEIR DEFINITION OF FLUKE LENGTH.

Figure 6.3 Percent of ultimate holding capacity mobilized versus normalized drag distance in mud.

VA •*. .*. . V . >. i -■- UM -••^•■..••-.^-.' -• '-- *■»-"-'-"-' -' •" '-' "»'- ■' I ■ Ai „I.J.J.-

17rr

SS

c 2 W

w D

8 10

ANCHOR AIR WEIGHT, WA (KIPS)

Figure 6.4 Fluke length versus anchor air weight for several drag anchor types.

26

40 50

'-%,"■ '-'.'■'. ' -"ÄfJ> ^\""- "•»• V V- .•" ■ '-■ V vv ■ v ■ '• V -' i-«>Tl,....-..v .... s. t. . ^ -s. N. -.-.. ■

POINT OF TANGENCY

f T

TO DETERMINE TENSION AT VESSEL:

TD = w(k + d)

where: w = mooring line weight per length

k = HD/w

d = water depth

TO DETERMINE CATENARY LENGTH:

s = [d(2k + d)] 0.5

Refer to NAVFAC DM-26 (Ref 2) for added details.

Figure 6.5. Catenary characteristics.

27

LJVLLHI) I ■Il'i"-'»*V^'---^it*-"- •'- ''-'-•-"'•-'f-'''ma -'•'-Ai • - Ü '- •'-*«'-'•»'•-**•-«'- * « - » - ft

7c. Determine :hain tension, Tr) (Figure 6.5)

7d. Determine required chain strength Tu = FS X Tp

OPTIONAL

NOTE STEP NUMBERING SEQUENCE SAME AS HOUND IN TEXT FOR OPTION I

Return tu 7b.

Determine anchor setting distance I).,, tu design load Sand D ■ J■ X I

Mud D . UD/, ) 'I.'

Ha Calculate catenary length s (Figure 6 51

8b Total chain length. 1

I - S («aiid/harduiill

Figure 6.6. Flow chart of Option 1 - Holding capacity curve design method.

28

•\ ,..,-.v.^.v.v.,.v..-, .-■ ■-■ '..\'

• - - -»•-»-• 'J- '■» - ■ • • »

[V

S 7. OPTION 2 - ANALYTIC MODEL

[Applicable only to muds and clays.]

Option 2 requires calculation of total holding capacity by anchor

system element. Calculation starts with anchor, then cutting chain,

followed by sliding chain. A flow chart of this procedure is provided

as Figure 7.1.

CUTTING CHAIN SLIDING CHAIN CHAIN OFF SEAFLOOR

__2_

DEFINITION OF SYMBOLS FOR ANCHOR-MOORING LINE SYSTEM

A. RANGE OF VALIDITY OF OPTION 2

Soil Strength Profile

The analytic method of Option 2 should be applied only to normally

consolidated cohesive soil profiles with a range of strength gain rates

(with depth) of 0.010 ksf/ft ± 0 003 ksf/ft.

This limitation does not apply to the method when the penetration

depth is known. The procedure for calculating the anchor holding

capacity, when the penetration depth and soil strength at the anchor ure

known, will be valid for a broad range of soil strengths, through the

soft clay range to the mid-medium strength clay range (i.e., up to an

undrained soil shear strength of 0.7 ksf).

29

>.>.,...,...V TV - - • >>;

AV..VV. ■ *--.«--«--o^'..' .A ■ 1 - » - < - L~ «^

Mooring Line Type

i->"

The analytic method (in particular the anchor penetration prediction)

is believed applicable only when the chain size is such that the chain

breaking load is 50% greater than the ultimate capacity of the anchor.

This situation exists when a factor of safety of 2 is used for design of

the anchor and 3 is used for the mooring chain. When the mooring line to

the anchor is wire rope or oversized chain, then the developed penetration

relationships are not valid; however, modifications to the developed pro-

cedure to account for these untested conditions are suggested in Section 7C.

-." B. PROCEDURE

Loads and Soil Description

1. Obtain loads as described for Option 1 (Section 6, step 1),

2. Identify seafloor material type (Section 2). In addition,

obtain undrained soil shear strength, s ,

laboratory tests on core samples (Ref 1).

obtain undrained soil shear strength, s , via in-situ tests or

Anchor Type and Size

3. Select anchor type (Tables 3.1 and 3.2)

4. Select anchor weight and calculate anchor ultimate holding

capacity, T AIT

a. Select anchor initial air weight, W.

JA = (0.75) ye

30

*-' "«'->->-'» -■•-*■•-V->-V- v;,;,:.:;:^^;^-:-^^:^

• '■.*>

whe re: H.. = required ultimate horizontal capacity

e = anchor efficiency (Table 3.2)

Or use Figure 6.2 at TM = 0.75 H.. to determine W„.

b. Obtain anchor fluke length, L (Figure 6.4).

c. Estimate fluke tip penetration, d., as lesser of:

(1) Maximum penetration, d. , at unlimited drag distance,

D (Figure 7.2 at D/L = 50).

(2) Penetration, d., at specified maximum allowable drag

distance, D.

Ö (3) Thickness of soil layer, t.

d. Obtain undrained soil shear strength, s , from step 2, at

depth d..

e. Obtain holding capacity factor, N fBL, from Figure 7.3.

f. Calculate anchor ultimate capacity, T AIT

TAU - su(Nc f BL)

where: N = holding capacity factor sensitive to plate

shape and depth (dimensionless)

f = factor converting the rectangular fluke area

B • L to true fluke area (dimensionless)

B = anchor fluke width

31

&^M^v^>^.^^.:.-> /iViV/.»^.^ra>w;'vIVJV^VAvy^..^

'* -*"J

ZK-

rsS

g. Check adequacy of anchor selection with respect to ultimate

capacity. If T. f (0.75 to 0.85) • H,,, then select new

anchor air weight and repeat steps 4c through 4g.

5. If maximum allowable design drag distance is specified, then

calculate anchor design holding capacity, TAn. A 50-ft allowable

drag distance to design or safe working anchor capacity is

typical for Navy fleet moorings. Initiate calculation with

anchor selection from step 4g.

• *■•

a. W», L, N fBL, and soil layer thickness available from

step 4.

b. Estimate fluke penetration depth, d., as lesser of:

(1) Fluke penetration, d., at design drag distance, D

(from Figure 7.2).

(2) Thickness of soil layer, t.

c. Obtain undrained soil shear strength, s , at depth dt.

S3

d. Calculate anchor design capacity, T AD'

TAD = Su<Nc f BL>

e. Check adequacy of anchor selection with respect to design

capacity. If T.D < (0.75 to 0.85) • HQ, then return to

step 4a and select larger anchor air weight. Repeat

steps 4 and 5.

32

•••»•■•■••-•-»•■ ■ -- •■

TV '-*• -% »*• *^»->»">- » ->-•|-»Vt .•»*.'».» .'..V'.l Al

Chain Size

6. Select chain size.

a. Estimate chain breaking load, T,,:

1.15 • FS • HD (FS = 3 for chain)

b. Select chain size, D (Table 6.2)

c. Calculate chain maximum tension, Tn (Figure 6.5),

d. Calculate chain required breaking load, T,:

(FS = 3 for chain)

e. Check adequacy of chain size.

TU = FS * TD

(1) If I"., differs significantly from chain breaking load

(Table 6.2), then repeat steps 6b through 6e with new

selection.

(2) Chain breaking load should be at least 1.5 • maximum

anchor-chain system capacity, L..

Anchor-Embedded Chain System Holding Capacity

7. Determine anchor system capacity, L., at maximum penetration.

a. Obtain depth of anchor end of chain, d , the lesser of:

(1) Maximum penetration, d , at unlimited drag distance,

D, (from Figure 7.4 at D/L = 50).

13

t-" •- ^' *-' «--«-' •>■* V ^ M '-• «V«

(2) Maximum penetration at specified maximum allowable

drag distance, D.

(3) Thickness of layer, t, minus one fluke length, L.

b. Obtain anchor-embedded chain capacity, L., fr ,m Figure 7.5.

Interpolate for intermediate chain sizes. NOTE: Figure 7.5

can be used to determine L, at any anchor drag distance.

c. Check adequacy of anchor selection with respect to

anchor-chain system ultimate capacity. If TM < H.,, then

select next larger anchor air weight and repeat steps 4b

through 4f and steps 7a through 7c.

d. Check adequacy of anchor selection with respect to

anchor-chain system design capacity if capacity is limited

by drag distance. Determine TMS = T^/FJ. If TMS > L,* at

a specified drag distance, use L, = L,<. and compare to H~.

If L. < Hp., select a larger anchor.

Total Chain Length

8. Determine total chain length from anchor to vessel fairlead.

a. Determine length of chain cutting into the seafloor, L .

Given L, and d from step 6, obtain L *rom Figure 7.6.

b. Determine length of chain in catenary, s (Figure 6.3). For

economy, use s at design, not ultimate load.

c. For optimum design, length sliding on seafloor, L., is

zero. See Section 8 to include sliding segment, L .

TM = T.Q (from 5d) + buried chain resistance.

;:o;>äfr:^::^^^ &tä.\täi ,x,,v:v;^

d. Total length of chain required, L., is:

Lt = Lc+Ls+S

9. Calculate anchor setting distance to design load.

a. Select D/L from Figure 6.3 at appropriate FS. FS = 2 is

recommended and values are provided.

Dp = L(D/L)

C. MODIFICATIONS FOR WIRE ROPE AND OVERSIZED CHAIN

The developed method for anchor penetration prediction is believed

to apply only for those chain-anchor combinations where the chain

breaking strength is about 50% greater than the anchor ultimate capacity,

When the mooring line to the anchor is wire rope or oversized chain,

then the following modifications are suggested to the holding capacity

prediction procedure.

Wire Rope

A wire rope mooring line will not develop significant holding

capacity, and its contribution can be ignored. However, the anchor in

this system will penetrate deeper, reaching stronger soils. It is

suggested that the holding capacity of the wire rope-anchor system be

assumed equal to that of the appropriate chain-anchor system.

To estimate the depth of anchor penetration for the wire rope

system, the entire system holding capacity, L., is assumed to be

developed at the anchor. Then the equation

su ■ V<NcfBL>

35

V-i

is used to determine the undrained soil strength, s , necessary to

develop that T., and the soil strength profile is examined to find the

soil depth at which that strength is found.

Oversized Chain

Oversized chain used in an anchor system will develop an increased

resistance to mooring line penetration because of its larger bearing and

frictional areas. Thus, penetration of the attached drag anchor will be

inhibited, and the holding capacity developed by the anchor itself will

be smaller (than with the normal-sized chain) because the anchor will be

in shallower, weaker soil. It is suggested, to be on the safe side,

that the holding capacity, L., of the oversized chain-anchor system be

assumed equal to that of the appropriate chain-anchor system. Then the

probable penetration of the oversized chain-anchor system is projected

through an iterative process.

For the first iteration the anchor penetration depth is reduced by

10% from that predicted from Figure 7.2. The anchor contribution at

this depth is computed from step 4f, and the contribution of the oversized

■JS chain is added using Figure 7.5. The system holding capacity from the

g first iteration, L,,, is then compared to the assumed holding capacity,

TM, and the assumed depth of anchor penetration is adjusted. The itera-

tions are repeated until the desired fit is achieved between L. and L. .

It is emphasized here that neither this suggested method for

treating anchor systems with oversized chain nor the method for wire

rope mooring lines has been validated in the field or laboratory.

>.

y

36

v.'

.■'.••'.■'.■.■•>'.^.v'.'".--'.

Step 5. not needed when maximum

allowable drag distance to design (safe) capacity is not specified.

I

from Step 4.

5b. Determine fluke tip

penetration, d(, at lesser of

1) dt = L (dt/l.) for D/. allowable

(Figure 7.2) 2)t

* Use Option 1

3. Select anchor type

(Tables 3.1, 3.2)

4a. Select anchor weight, W, .

To initiate use Figure 6.2 AT T =0.75H„

4b. Determine fluke length, L (Figure 6.4)

1' dt as lesser of:

(l)dt*atD/L-50

(2) d * at maximum allowable

(3) soil thickness, t

•V,.("t/J

% 4c. Determine fluke tip

penetration, d

(Figure 7.2)

.

' t

4d. Select Su at d,

- from Step 2.

' ' 4c, Determine N . f Bl.

(Figure 7.3)

< ' 4f. Calculate TAU,

TAIJ = su<Nc(BI.)

Yes Return in 4a.

Select new anchor wt.

t> Si/c chain

6u Ksttnuit required chain

strength

T FS = 3 recommended tor chainj

Figure 7.1. Flow chart of Option 2 • Analytic Model.

37

.V.-..VV . \,"*. - . •. .- >.N.%.V-. ..-..-. a ^ '-A .•„ J-. J-

(continued from previous page)

OPTIONAL

Added capacity of sliding chain

For existing systems where chain leg

length is established, calculate added capacity of sliding surface chain. (Usually small and can be ignored)

1 ' Ls * lt - tc • S

or

Ls - Lc - Lc

' ' Determine H,

(Table 8.1)

' < Calculate T

T$=LS-M*W

W -from Table 6.2

> Calculate T.,

Tll ■ ' M * 's

6b. Select chain size, Dc

(Table 6.2)

No

1 6c Determine chain tension, T~

(Figure 6.5)

1 6d. Determine required

chain strength

TU • FS * TD

< 6eTu-L5TM >=

, Yes ds as lesser of

(l)ds'at D/L = 50

(2) ds*at maximum allowable "/\

(J)t-L

7a. Determine chain end depth, d

(Figure 7.4)

" 7b. Determine TM

(Figure 7.5)

■► Return to Step 4a.

8a. Determine L

(Figure 7.6)

8b. Determine catenary length, S,

(Figure 6.5)

OPTIONAL

8d. Total chain length

Determine anchor

t* setting distance 1)

to design load /T -(iy ) taken at\ |

—( design FS 1 t

v-CvJ \. (Figure 6.3) S |

NOTF Step numbering sequence same as found in text for Option 2.

Figure 7.1. Continued

38

**«L *±m ti -» - - .^-->._..--...--. .•-•■-•-'

* ANCHORS REQUIRE SPECIAL HANDLtNG (POSSIBLY FIXED FLUKES) TO ENSURE TRIPPING IN SOFT CLAYS AND MUDS.

' -^jOCKLEss «PVAfir.c-

FLUKE

c .TOCKLESS FIXED FLUKE

*-42iT0

-£°p* ^-StüL£HAWK

^MUD — 1 Ji

»« r*nnr- nrp^Hicc r^ Annirr-c

:ATER.

WHEI FOR DRAt

< FLUKES MOVABLE DISTANC

FIXED 0 FLUKES E IS 1.

SEN. rOTAL x L GR

10 50

D/L

Figure 7.2 Predicted normalized fluke tip penetration versus normalized drag distance.

tu

IS

8 10 40 60 80 100 200 40o" 600 8001000

ANCHOR AIR WEIGHT W„ (KIPS) A

Figure 7.3 Anchor holding capacity factor, NcfBL, versus anchor air weight, W^, based on anchor designs available in June 1982.

39

• ^ t ^ i l^__^_^jjjl-l-i-iili—liiJJ—LLLLJ " I " *'~ '■"• •■A* '■*-A^"---"«-•---'-' . •«.-. ■ v-. •. • .i. i» .-.• CMAM2 -..• »-1»JI «■

D/L

> 3

'For prc-set or fixed open flukes

Figure 7.4 Normalized shank tip penetration versus normalized drag distance for eight anchor types.

40

-"■'-•■'■'-''-,-''^ --'- J'-J"•"-•'•■''•■'»'•■ »■•'«>'■>■>-V-- • ■■-'■

TB *~ 40 60 80 100 " 200

ANCHOR TENSION, TA(KIPS)

400 600 800 1000

1000

800h

600 •

400-

100

80

Z 60

20

10

n— i 1 i i i i i ' I 'IT ■T T i ■ i T 1 1

■ I ' J~ '

- t/1

M~"" BREAK LOAD-OIL _, • ■

«W _^*^^ m* Kll. UUA L1TY C HAIN "

: _^' ^ 2 - INCH CHAIN ■

■ "<A -

• d = DEPTH T

S

1 DENOTES

0 SHAf

0 - «

K TI

0°

P, FT

•

6 ^sdßr

■

■ ; " I

■ llP/. // ■ •, ■

■ ^ ■

• iH ■

■

yv ■

■ \pVA tb) FOR 2 INCH CHAIN

* << W. 1 i, i

"

6 8 10 20 40 60 80 100 200

ANCHOR TENSION, Tft(KIPS)

400 600 800 1000

Kigurc 7.5 Tension at mudline versus tension at anchor.

VI

-» -* -•■-•* -'-•-» ■• ,•> i~i -i .• -■

1000

aoo

600

400

20

- ' 1 ~T 1 »' ■ * ■ ' ' i

1 ' "252 - AW-- ■ T gz • M

* Ml {> L1 N E ? ■ ^W^^T _n^^^^^^^^^^ ^W^P

- Sv\ j^ ■

<7T >^ ■

■ d = UfclFTH TO SHANK TIP, FT s Mi ^/^

■

■

B =

&t <' /,

-

- S.' - ■ • < - - •j - ■ > - - V ' > - - t •" > ^ - • yyj

^ •

- 'S ■ (c) FOR 3 INCH CHAIN

P 4

' _i o 8 10 20 40 60 flO 100 200

1000

800

60o|-

„ 400

200

20

,n4

. 1 ■ 1 r T ' 1 ' 1 ' "T" -T- T T 1 1 T- -r-

* ■

■ T

'■ T3

,4 % V - SSZHf -*****^ v ■

dTY M - INCH CHAIN i - ■ A ! '_///t

f - d

£

1

= DEPTH T

DENOTES

3 SHAN

6 - 9

( TI

0°

9, T \?M *Jy/

■

• y >

/jar

■ / . • rf' . l iV ■ LP'J . • ^ ■

• iV> 'S/ ■

• ■

■ • (d) FOR 4 INCH CHAIN

^ I 1

A V .1 i

■

' 6 8 10 20 40 60 HO 100 ?00

ANCHOR TENSION, Tft{KIPS)

400 600 B00 1000

Figure 7.5 Continued

U1

v.v.v. .-.v.v. «■•...-,.«.-. .-.•.•..•.-.■«.•.._ _ • » - . .. - - • -._ -_- v- . .. ... -v %.- »■•>.•-.••■--■•■%■• i - - - » - Li *- ■

m 1000

800

600

400

200

100

20;

■ ' * * ^-_r ' ' • —r-

• (a) FOR 1 INCH CHAIN

■

■ _ • ■ • ■ -

T ■ M

■100KIPS BO

•

^jj 40

•

„>* **•* ■

/Vl ^ ^^*~ 1 . • <H ^H ̂ . >io • ^x -^ T*

■

^ J ̂ ■

- r y 1-INCH CHAIN^ TM^ ■

^ . ds ■

^ T

M = TENSION AT MUDUNE

1 DENOTES 8 = 90° 1.1 . I.I.I,

KIPS

,1, ■

,,, 4 6 11 20 40 60 80 100

SHANK TIP DEPTH, d (FT)

1000

800

600

500

400

300

t- 100 3 U 80 X H

5 so 50

2 2 40

30

20

1 ' —1— T J ' ' ' 'i' ~T T T

T.. ■

■

(b) FOR 2 INCH CHAIN M

1000 KIPS- ■

' 800 600t--

1 M00--

1 • ■

--^^rf — -

1 n 0

0

J 40

J 8 60 ■

'^^^ J _s>

^J 20 ' ■

I 1 1

■^^^^**

0 _u ' T

2-INCH CHA IN^p Sj__ 1 .

^s^ d

N AT ^

t' = <i

1 .

S

l_ 4— — i .—*.- —*_ _ —*i-i

TM * TENS IL

, 1 DENOTES

1UDLI

0°

N;E

L. IK

L L )

llL 1 i j 4 b 6 7 t 9 10 20 30 40 50 60 80 100

SHAW TIP UEPTH , d (FT) s

Figure 7.6 Length of chain cutting into soft clay scafloor versus depth of anchor shank tip. Chain assumed tangent to scafloor at mudlinc.

A^j^^^^^^^y^^t^^^üakS^Ci^^^ A ^ik --'■'-v*'""""-■ '"-* '•-■/j - - ^ •-» jt *- v- i.

v*^

800

1000 KIPS

4 6 11

SHANK TIP DEPTH, d (FT

TM - TENSION AT MUDLINE (KIPS)

10° | , I ■ I . I .1 ,1 .1.

40 6080 10

1 DENOTES (' • 90

L^ i ■ i ■i 20 100

11 20 40 60 80 100

TIP DEPTH, d (FT)

Figure 7.6 Continued.

4 4

t^^m •ill! I

8. ADDED HOLDING CAPACITY FROM SLIDING CHAIN

A. APPLICATION

An optimum design uses the anchor and embedded or cutting chain to

develop the necessary holding capacity. The use of additional chain, to

lie on the seafloor and provide added "frictional" resistance, is

generally not a cost-effective way to develop added necessary system

holding capacity. Generally, anchor system capacity is best increased

by increasing anchor size rather than chain length. However, for those

situations where nonoptimum choices must be made, the following guidance

is given for the prediction of the sliding resistance of mooring line

lying on the seafloor, L . Refer to Section 7, page 29 for definitions.

B. PROCEDURE

1. Calculate length of sliding mooring line, L .

a. Options 1 and 2:

(1) On sand seafloors,

Ls ■ Lt-s

(2) On mud seafloors,

Ls ■ Lt - (s ♦ Hu)

where: H.. = ultimate horizontal holding capacity

in kips

45

'£ü&Ää&2Ütä •_ »•. «". £- «V ». Aft".

b. Option 3:

Ls - Lt - (s + Lc)

2. Calculate friction force, Ts, developed by sliding section of

mooring line.

Ts = Lswp

where: w = weight of mooring line per unit length from

Table 6.2

ii = friction coefficients from Table 8.1.

3. Calculate total horizontal holding capacity, T„:

TH = TM+TS

46

i^_«. _j» _ — ■ A ^$Lm.\ - \ - * —* ■ i^ii^^;^:^^^

Table 8.1. Recommended Friction Factors for Mooring Line

Mooring Line

Ocean Bottom Friction Factors, y

Starting Sliding

Chain

Wire Rope

Sanda

Mud With Sanda

Mud/Clay

Sand3

Mud With Sanda

Mud/Clay

0.98

0.92

0.90

0.98

0.69

0.45

0.74

0.69

0.56

0.25

0.23

0.18

'(from Ref 3)

4 7

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-.'■> --V-.-.

fc

^ T »

;<£!

">

"A

9. IMPROVING ANCHOR PERFORMANCE

Anchors do not always behave as predicted. Table 9.1 provides

guidance that was derived from analysis of field anchoring problems to

enable field corrections to poor anchor behavior. Figures 9.1

through 9.4 illustrate some of the problems described in Table 9.1.

48

fr^:^>>^v:-;^r:^^

Table 9.1. Ways to Improve Anchor Performance

'.' *

Problem Symptom Possible Reason Possible Solution

Poor mud • Near constant line • Flukes not tripping • Increase size of tripping

performance tension 1/2 to 2 palms; add stabilizer

times weight of anchor • Weld or hold flukes in

and mooring line on open position and place

seabed (see Figure 9.1) anchor right-side-up

• Drop in tension during • Anchor unstable • Add stabilizers

proof-loading with • Increase stabil!^, length

continued drag • Use different or larger

anchor

• Soil more competent • Reduce fluke angle to sand

than anticipated setting or if possible by

a smaller amount (5 to

10-c". g reduction)

• Proof-load tension • Seafloor softer • Use larger anchor

less than needed than expected • Use different anchor

• Less sediment than • Add chain

needed over harder • Use backup anchor

substrata

Poor sand/ • Near constant tension • Flukes not tripping • Sharpen fluke tips; add

hard soil 1 to 3 times weight of fluke tip barbs to break

performance anchor and mooring up soil

line on seabed • Weld or block flukes in

(Figure 9.2) open position

• Extend anchor crown by

lightweight pipe or

plate construction

• Water jet anchor flukes

into seabed

• Variable tension 3 to • Flukes not penetrating • Reduce fluke angle; reduc-

10 times weight of tion to as little as 25 deg

anchor and mooring may be needed for very

line on seabed dense or hard soils

(Figure 9.3) • Sharpen flukes

• Extend or add stabilizers

• Use larger or different

anchor

• Rapid drop in tension • Anchor unstable • Extend or add stabilizers

during proof-loading • Use larger or different

with continued drag anchor

(Figure 9.4)

c Proof-lead tension • Less sediment than • Use larger or different

less than needed needed anchor

• Very hard seafloor • Add chain

• Use backup anchor

• Use pile anchor

.*»*.

•

Anchor failing to trip and sliding on soft bottom.

Figure 9.1 Potential anchor problem on soft mud seafloors when anchor is not properly set.

Anchor dragging on hard scafloor with fluke tips unable to bite in.

Figure 9.2 Potential anchor problem on hard seafloors.

S(i

■••-•---■>•■»■■■-•--■ - - ■■ *■'* ' -* •- -- •-'■ ' i «-*■ «-' hi «-'■ '- -' fc '-' -' «-' -' *-*■»-' *- *-* *-' *-

Anchor standing up but tipping to side and dragging.

Figure 9.3 Potential anchor problem in hard seafloors when fluke angle is too large (after Ref 4).

(a) Unstabilized Stockless anchor rolling in sand (after Ref 4).

(b) Properly stabilized anchor in sand (after Ret 4).

Figure 9.4 Function of stabilizers in sand.

rW

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j£^£jJljllJjjl<_L«.ifI V» 1 ' '"' i 1 ''•-*'•-*'*-" - ' i.' » 1 »'-•»' *** »•«•»•>-•-■■ ■«-' ■»■' ■»

, I".

10. EXAMPLE PROBLEMS

A. EXAMPLE DESIGN FOR SAND

A drag embedment anchor system is required to resist a survival

horizontal line load of 60 kips. Water depth is 60 ft. Maximum drag

distance allowed is 50 ft. The owner has Danforth and LWT anchors in

storage.

Option 1 - Holding Capacity Curve Option (refer to Section 6)*

1. Calculate H..:

a. Hp. = 60 kips

b. FS = 2.0 (Section 5)

c. H(J = 2.0 • 60 kips = 120 kips

2. Identify seafloor material type: Medium dense sand of minimum

12-ft thickness.

3. Select anchor types: Danforth and LWT anchors are both good

types for this application (Tables 3.1 and 3.2). In sand,

e = 11.

"Numbering sequence is the same as found in the procedure.

52

*■.* •,' %' •« ■. *«_*•.-."*. ■ •'•y • \' v vv . •<■.•'.»«.«■ ■ - • ■ • • :.: ■•■: .viv:-. :••:•! y.y.v.y.: ^^;^^w^i^v^v^-:v:%^v.^ .N.-.-.

4. Select W. and calculate L.:

a. Select W,

At TM = Hy - 120 kips, WA = 9.0 kips (Figure 6.1)

Select 9-kip LWT

NOTE: POSSIBLE TO SKIP TO STEP 6 FOR MOST ROUTINE

MOORINGS.

b. Determine TM for selected anchor. M

TM = 120 kips; the 9-kip size is coincidentally the

exact choice for Hi., = 120 kips.

5. Check adequacy of drag distance.

a. Adjustments to T„:

L = 6.8 ft (Figure 6.4)

For fixed flukes,

D = (D/L) • L = 8 • 6.8 ft = 54 ft = 50 ft allowed

Assume this selection of a 9-kip LWT is satisfactory.

b. Check of selection adequacy:

TM (200 kips) > Hy (200 kips), satisfactory.

NOTE: This step was unnecessary since no adjustments were

made to Tu and anchor selection. M

Si

-» -=-•-•■■■». * .»-■-»«.»-» ■•» --.

6. Check adequacy of soil thickness.

a. dt = L = 7.4 ft (Table 6.1).

b. In sands, full penetration is assumed necessary.

c. d. < t? (t = 12 ft, step 2). Satisfactory.

7. Select chain size:

a. T, 1.15 • FS • Hn = 1.15 • 3.0 • 60 kips = 207 kips

f.** b. D selected is 1-3/4 in. (Grade 2); breaking load = 247 kips

(Table 6.2). Assumes the 1-3/4 in. size is more readily

available than smaller, but also adequate, sizes.

v<4 c. TQ = w (k + d) (Figure 6.5)

w = 0.0302 kip/ft

k = 60 kips/0.0302 kip/ft = 1,987 ft

60 ft

TD = 0.0302 kip/ft (1,987 + 60) = 61.8 kips

d. TJJ = FS • TD = 3.0 • 61.8 kips = 185.4 kips

e. Chain adequacy:

(1) Tu << chain breaking load. If available, lighter

chain may be appropriate.

(2) Chain breaking load (247 kips) » 1.5 TM (180

kips): satisfactory.

34

:-:vSfcöflfc£^£%^

£■*.>

*»

8. Determine chain length:

a. s = [d(2k + d)]0'5 = [60 ft (2 • 1,987 + 60)]0'5 = 492 ft

b. L. = 492 ft. Calculate number of shots:

n = 492 ft/90 ft = 5.5

Therefore, 5-1/2 shots per leg.

9. Determine anchor setting distance:

D = 3L = 3 • 7.4 ft = 22.2 ft P

Summary - Example Design for Sand

Anchor size selected 12-kip Stato

Chain size selected 1-3/4 in.

Predicted capacity: ultimate 132 kips

Chain length required/leg 492 ft

B. EXAMPLE DESIGN FOR SOFT CLAY

A drag embedment anchor system is required for a class C mooring

(design capacity of 100 kips per leg) on a soft clay bottom. The soft

clay is known to be normally consolidated and 60 ft thick. Maximum

allowable drag distance for anchors to design capacity is 50 ft.

Anchors will be blocked open to eliminate tripping distance. Water

depth is 120 ft.

55

m— i'-w..^.^!^^ ■■■■V.,.-.,.'.,.VfVv-:.',t.\-..•••.• v •.-'•.• -.- .. '.V...... V .■.•.*• - •■■■■■ . ■•-. v . ..• i .«- j «- <

OPTION 1 - Holding Capacity Curve Option (refer to Section 6)

1. Calculate H..:

a. Hn = 100 kips (design horizontal load)

b. FS = 2.0 (Section 5)

c. Hy = 2.0 • 100 kips = 200 kips

NOTE: The design capacity of 100 kips must be attained within

the allowed 50 ft of drag. However, anchor drag distance

greater than 50 feet is acceptable to develop the required

200-kip ultimate capacity.

2. Identify seafloor material type: Soft clayey silt (mud) of

minimum 60-ft thickness (sediment thickness derived from

acoustic reflection data).

3. Select anchor type:

a. The better performing anchors in soft clays and clayey

silts (muds) are Stato, Stevfix, Stevmud, Boss» and Hook

(Table 3.1). The Stato is selected because it is available

in stock.

b. In mud, e = 20 (Table 3.2)

4. Select and calculate T M"

a. Select anchor air weight:

For TM = Hy = 200 kips, WA = 9.0 kips (Figure 6.2)

Use 9-kip Stato for first trial

56

K c'^>^^ -** "*» 1» • - " . •- < - - * - . - W -. . ^I^T-T-«.

NOTE: POSSIBLE TO SKIP TO STEP 6 FOR MOST ROUTINE MOORINGS

b. TM s 200 kips for the 9-kip Stato (Figure 6.2). The 9-kip

Stato is the exact choice for H., = 200 kips.

5. Check adequacy of drag distance.

a. Adjustments to L,: Limitation of drag distance of 50 ft

requires check of design capacity.

L(9-kip Stato) = 8.3 ft (Figure 6.4)

D/L = 50/8.3 - 6.0

r = 51% (Figure 6.3)

TM(50 ft) = °"51 * 200 kips = 102 kips

b. Check adequacy of anchor selection:

(1) TM (200 kips) > Hu (200 kips); Yes, Satisfactory

(2) TMS = TM/2 = 100 < TM(50 ft) = 102 kips

Use TM = TMS = 100 kips

TM >_ HQ (100 kips); Satisfactory

6. Check adequacy of soil thickness:

a. dt/L = 4.5 (Table 6.1)

b. dt = 4.5 • 9.4 ft = 42 ft < 60 ft; Satisfactory

5 7

fe^v^>^:^:^^^^fe^.>■-*<:: ^^::^^:;^c:-^s^ • V • .' -• ." V -" • -" •" • . - - . ■ \-Vv\-v\ -. --W -". -%. -"W Al

7. Select chain size:

a. Lj = 1.15 • 3 • 100 kips = 345 kips

b. D = 2-1/4 inches, Grade 2 chain with breaking load of

396 kips (Table 6.2)

c. Tp. (catenary) = w(k + d) (Figure 6.5)

w = 0.0495 kip/ft (Table 6.2)

k = 100 kips/0.0495 = 2,020 ft

120 ft

TD = 0.0495(2,020 + 120) = 105.9 kips

d. Ty = 3.0 • 105.9 kips = 317.7 kips

e. Chain adequacy:

(1) Ty (317.7 kips) « breaking load (396 kips), 2-1/4-in.

chain satisfactory. Note, 2-in. chain (breaking

load = 318 kips) may also be suitable. Could repeat

steps 7c and 7d for 2-in. chain.

(2) Check: Chain breaking load (396 kips) » 1.5 T

300 kips), satisfactory. M

8. Obtain required chain length:

a. s = [d(2k + d)]0,5 = [120(2 • 2020 + 120)]0'5

= 707 ft (Figure 6.5)

58

*M •\ --. •.--.,«-

•' ■' - ill ji*ii'- tiMM *"■•-*'• ■'■■" '■* ** Ü'' •-«•-*•'-■ J - » -■•-- -^> ---• - •-•.•-V-V/.--V-V-V-.V.V-■ \:r\,:»\f~*\

V13

b. Lt (soft seafloor) = s + ^ - 707 + 200 = 907 ft.

Calculate number of shots:

n = 907 ft/90 ft = 10

Therefore, use 10 shots per leg.

9. Determine anchor setting distance:

Dp = (D/L)*L (Figure 6.3)

ft

(D/L) (for Stato at FS = 2)

D = 6 • 8.3 ft = 49.8 = 50 ft

Option 2 - Analytic Model (refer to Section 7)

1. Calculate H,.: Same as Option 1 example.

H u = 200 kips

2. Obtain soil strength profile (presented in Figure 10.1): from

laboratory vane shear tests on high quality gravity corer

samples.

3. Select anchor type: Same as Option 1 example.

Use Stato.

5"

4. Calculate anchor ultimate capacity, T...:

a. WA = 0.75 Hu/e = 0.75 • 200 kips/20 (e from Table 3.2)

7.5 kips

Next largest Stato manufactured is 9.0 kips.

L-f. Use 9-kip Stato.

b. L = 8.3 ft (Figure 6.4)

c. Fluke embedment, d.:

d. /L at full penetration = 4.5 (Figure 7.2)

d. = 4.5 • 8.3 ft = 37 ft tm

t of soil = 60 ft d. = 37 ft tm

dt = 37 ft

d. s = 0.37 ksf at d. (Figure 10.1)

e. N f BL = 510 ft2 c (Figure 7.3)

f. T AU -u c

s„ N f BL = (0.37 ksf)(510 ft2) = 189 kips

g. TAU = 189 kips is greater than (0.75 to 0.85) Hy = 150 to

170 kips. The next smallest Stato is 6 kips. It was not

adequate.

M)

•-•-WWltaV

• . " * -j- VV-.-V I ■ ■ - ■ - ■• ■•>•■. - ■

w

5. Check adequacy of anchor selection at 50-ft design drag distance.

a. W., L, N fBL, and t available from step 4.

b. Fluke penetration depth, d •

(1) D/L = 50 ft/8.3 ft = 6.0

dt/L = 2.5 (Figure 7.2)

dt = 2.5 • 8.3 ft = 21 ft

(2) Soil layer thickness, t = 60 ft >> d.

Thus, dt = 21 ft

c. su = 0.21 ksf at dt (Figure 10.1)

d. TAD = su Nc f BL = (0.21 ksf)(510 ft2) = 107 kips

e. T.pj = 107 kips is greater than (0.75 to 0.85) HD = 75 to

80 kips. As stated in 4g, the next smallest Stato (6 kips)

was not adequate. Therefore, a 9-kip Stato is satisfactory.

6. Size chain: Same as step 7 in Option 1 example.

2-1/4-in. chain selected.

7. Determine anchor-chain system ultimate capacity, L,:

a. Chain embedment depth, d , as lesser of:

(1) d /L at maximum penetration = 3.6 (Figure 7.4)

dcm = 3.6 • 8.3 ft = 30 ft sm

61

L^-"wL»-i^L '-] ■ -' ■ '■-•-•--'■-*■-■ ------. •-- •■*. '-It 'J *-■>•-» -A,'.- •-- ..-

* ' ■ * • ' - • ~ * - * - » " m "m "' j

(2) Not required

(3) Maximum possible shank penetration:

t - L » 60 ft - 8.3 ft = 52 ft

Thus, ds = 30 ft

b. ForTAU = T L = 189 kips; use Figure 7.5 to find T.

2-in. chain, T.. = 230 kips

3-in. chain, L. = 235 kips

c. For 2-1/4-in. chain, TM = 231 kips > 200 kips; satisfactory.

d. Check L. at 50-ft design drag (refer to steps 7a and 7b).

TAU = 107 kips (from step 5d) > HQ (100 kips)

L.* > T-c; therefore TM > 100 kips; satisfactory.

The calculations are done for example:

Chain end embedment, d , at 50 ft:

D/L = 50 ft/8.3 ft = 6.0

d$/L = 2.1 (Figure 7.4)

d$ = 2.1 • 8.3 ft = 17.4 ft

*L, = T.ß + resistance provided by buried chain.

62

£3£ 11 liiailf *** *'* '"***■ <*■ i*> «■ i*'

151 •r,

Maximum possible shank penetration (from step

7a(2)) = 52 ft.

Thus, ds = 17.4 ft

For T.p. = T. = 107 kips, use Figure 7.5 to find T.

2-in. chain, TM = 125 kips

3-in. chain, TM = 130 kips

For 2-1/4-in. chain, 1»/™ f.» = 126 kips > 100 kips;

satisfactory.

TMS = TM(ultimate)/2 = 231 kiPs (from steP 7c)/2 = 115 kiPs

TMS (115 kips) < TM(50 ftj (126 kips)

Use TM = TMS ■ 115 kips

TM ■> HQ (100 kips); satisfactory.

8. Chain length required.

a. Length of chain cutting into the seafloor at ultimate load

of TM = 200 kips.

At d = 30 ft (step 7c), use Figure 7.6 to find L :

6J

....... ... •.•■•-•.-..'..--,..

2-in. chain, L = 250 ft

3-in. chain, L = 220 ft c

2-1/4-in. chain, L = 242 ft c

b. Catenary length, s = 707 ft (from Option 1, step 8),

c. Design for L = 0 j s

d. L. = L + L + s = 242+0+707 = 949 ft t c s

n = 949 ft/90 ft = 10.5, use 10-1/2 shots per leg

9. Determine anchor setting distance:

D = 6-8.3 s 50 ft (Figure 6.3)

SUMMARY - EXAMPLE DESIGN FOR SOFT CLAY

Anchor size selected 9 kips 9 kips

Chain size selected 2-1/4 in. 2-1/4 in

Predicted capacities:

at 50-ft drag 102 kips 126 kips

ultimate 200 kips 231 kips

Chain length required/leg 907 ft 949 ft

64

I ii i 1 •vÄ»»j»*-i'-> 1«.' «-* » T «-1 m.'

'"■"■"• -•-•'■

>..-»■■. . \^\m.l , ■ -«-«-»■•-»_«-»...

UNDRAINED SOIL SHEAR STRENGTH, S (KSF)

oc

5

.. L .2 3

£

10 W Z H ►J p D s

15 s o ►J w m a £H 20 0< W Q

25

Figure 10.1 Assumed shear strength profile for Option 2 soft clay example problem.

r>5

■' '-" --1- -• '-• t _. M .. «fc — • — «-*..< - * ~ % - ■ ...t».-._-» ; »«•

11. REFERENCES

1. K. Rocker. Handbook of marine geotechnology, Naval Civil Engineering

Laboratory. Port Hueneme, Calif., (in publication).

2. Harbor and coastal facilities, Naval Facilities Engineering Command,

NAVFAC Design Manual DM-26. Washington, D.C.

3. Recommended practice for the analysis of spread mooring systems for

floating drilling units, American Petroleum Institute, API RP 2P.

Dallas, Tex., May 1982.

4. Vryhof Ankers BV. Vryhof Ankers advertising brochure, Holland,

1980.

bb

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12. LIST OF SYMBOLS

B Anchor fluke width (from manufacturer's literature)

D Anchor drag distance

d Water depth

D Chain size c

■f\ DMAX Drag distance to peak load

D Anchor setting distance

d Anchor shank tip penetration

d Maximum shank tip penetration sm

d. Anchor fluke tip penetration

d. Maximum fluke tip penetration

e Anchor efficiency

f Factor converting the rectangular fluke area B • L to true fluke area (dimensionless)

FS Factor of safety

hL Maximum design horizontal load

H|. Ultimate horizontal holding capacity

k Coefficient equal to hL/W for catenary equation

L Fluke length

L Length of chain cutting into seafloor

L Total chain length in contact with seafloor e 3

L Length of chain lying on seafloor surface

L. Total chain length required

n Number of shots of chain

N A holding capacity factor sensitive to plate shape and depth c (dimensionless)

r Percentage of L, mobilized

$

67

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'S s

s

SPT

Su

t

TA

TAD

TAU

'MS

w

W,

Catenary length

Standard penetration resistance

L'ndrained shear strength

Soil thickness

Anchor capacity

Anchor design capacity

Anchor ultimate capacity

Chain maximum design tension at top of catenary

Total horizontal holding capacity (anchor + buried and surface chain)

Anchor-chain system mudline capacity

Safe anchor-chain system mudline capacity

Chain friction force due to surface chain

Chain required breaking load

Mooring line weight per unit length

Anchor air weight

Yb

Chain angle relative to horizontal

Bulk wet density of soil

Coefficient of friction between chain and seafloor (dimensionless)

68

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DISTRIBUTION LIST

AFB CESCH. Wright-Patterson ARCTICSUBLAB Code 54, San Diego. CA ARMY BMDSC-RE (H. McClellan) Huntsville AL; DAEN-MPE-D Washington DC ARMY COE Philadelphia Dist. (LIBRARY) Philadelphia, PA ARMY CORPS OF ENGINEERS MRD-Eng. Div.. Omaha NE; Seattle Dist. Library, Seattle WA ARMY CRREL A. Kovacs, Hanover NH; Library, Hanover NH ARMY DARCOM Code DRCMM-CS Alexandria VA ARMY ENG WATERWAYS EXP STA Library, Vicksburg MS; Coastal Eng Rsrch Cntr, Vicksburg. MS ARMY ENGR DIST. Library, Portland OR ARMY ENVIRON. HYGIENE AGCY HSE-EW Water Qual Eng Div Aberdeen Prov Grnd MD ARMY MATERIALS & MECHANICS RESEARCH CENTER Dr. Lenoe, Watertown MA ARMY MOBIL EQUIP R&D COM DRDME-GS Fuel Tech Br, r't Belvoir. VA ARMY TRANSPORTATION SCHOOL Code ATSPO CD-TE Fort Eustis, VA ASST SECRETARY OF THE NAVY Spec. Assist Submarines, Washington DC BUREAU OF RECLAMATION Code 1512 (C. Selander) Denver CO CNM MAT-0718. Washington, DC; NMAT - 044, Washington DC CNO Code NOP-964. Washington DC; Code OP 323, Washington DC; Code OP 987 Washington DC; Code

OPNAV 09B24 (H); Code OPNAV 22. Wash DC; Code OPNAV 23. Wash DC; OP-23 (Capt J.H. Howland) Washinton. DC; OP987J, Washington, DC

COMCBPAC Operations Off, Makalapa HI COMDEVGRUONE CMDR San Diego. CA COMNAVBEACHPHIBREFTRAGRU ONE San Diego CA COMNAVSURFLANT Norfolk, VA COMRNCF Nicholson, Tampa, FL; Nicholson, Tampa, FL COMSUBDEVGRUONE Operations Offr. San Diego, CA NAVSURFPAC Code N-4, Coronado DEFENSE INTELLIGENCE AGENCY DB-4C1 Washington DC DEFFUELSUPPCEN DFSC-OWE (Term Engrng) Alexandria, VA; DFSC-OWE, Alexandria VA DOE Div Ocean Energy Sys Cons/Solar Energy Wash DC DTIC Defense Technical Info Ctr/Alexandria, VA DTNcr>DC Ar.r.a Lab. Code 2724 (D Bluuxiiiju™} A.mapoiis. MD HCl JNE CO. Bishops Point. HI LIBRARY OF CONGRESS Washington, DC (Sciences & Tech Div) MARINE CORPS BASE PWO, Camp Pendleton CA MCAS Facil. Engr. Div. Cherry Point NC; CO. Kaneohe Bay HI MCRD SCE, San Diego CA MILITARY SEAL'FT COMMAND Washington DC NAF PWO, Atsugi Japan NALr OINC, San Diego, CA NARF Code 1(H), Cherry Point, NC; Equipment Engineering Division (Code 61000). Pcnsacola, FL NAS PWD - Engr Div. Oak Harbor. WA; PWD Maint. Div.. New Orleans. Belle Chasse LA; PWD. Code

I821H (Pfankuch) Miramar, SD CA; PWO Belle Chasse. LA; PWO Key West FL; PWO. Glenview IL; SCE Norfolk, VA

NATL BUREAU OF STANDARDS Kovacs, Washington. DC.; R Chung Washington, DC NATL RESEARCH COUNCIL Naval Studies Board/Washington DC NAVACT PWO, London UK NAVAEROSPREGMEDCEN SCE, Pensacola FL NAVAIRDEVCEN Code 813. Warminster PA NAVCOASTSYSCEN CO, Panama City FL; Code 715 (J Quirk) Panama City FL; Code 715 (J. Mitdeman)

Panama City. FL; Code 719. Panama City. FL; Library Panama City. FL; PWO Panama City. FL NAVCOMMAREAMSTRSTA SCE Unit 1 Naples Italy; SCE. Wahiawa HI NAVCOMMSTA Code 401 Nea Makri, Greece; PWD - Maint Control Div. Diego Garcia Is.; PWO. Exmouth.

Australia NAVCONSTRACEN Curriculum Instr. Stds Olir. Gullport MS NAVEDTRAPRODEVCEN Technical Library. Pensacola. FL NAVELEXSYSCOM Code PME 124-61. Washington. DC; PME 124-612. Wash DC NAVEODTECHCEN Code 605. Indian Head MD NAVFAC PWO. Centerville Beh, Ferndale CA NAVFACENGCOM Alexandria. VA; Code 03 Alexandria. VA; Code 03T (Essoglou) Alexandria. VA; Code

0453 (D. Potter) Alexandria. VA; Code 0453C. Alexandria. VA; Code 04AI Alexandria. VA; (ode 09M54. Tech Lib. Alexandria. VA; Code OKI Alexandria. VA; Code KKI2B (J. Leimanis) Alexandria. VA; Code 1113. Alexandria. VA

69

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L"V\-,

NAVFACENGCOM - CHES DIV. Code 407 (D Scheesele) Washington, DL; Code FPO-1C Washington DC; Code FPO-1E, Wash. DC; FPO-1 Washington. DC; FPO-1EA5 Washington DC; FPO-1P/1P3 Washington. DC; Library, Washington. DC.

NAVFACENGCOM - LANT DIV. Eur. BR Deputy Dir, Naples Italy; Library. Norfolk. VA; RDT&ELO 102A. Norfolk. VA

NAVFACENGCOM - NORTH DIV. (Boretsky) Philadelphia. PA; CO; Code 04 Philadelphia. PA; Code (MAL, Philadelphia PA; ROICC. Contracts, Crane IN

NAVFACENGCOM - PAC DIV. CODE 09P PEARL HARBOR HI; Code 402. RDT&E, Pearl Harbor HI; Library, Pearl Harbor, HI

NAVFACENGCOM - SOUTH DIV. Code 90. RDT&ELO, Charleston SC; Library. Charleston, SC NAVFACENGCOM - WEST DIV Code 'MB San Bruno. CA; Library. San Bruno, CA; O9P/20 San Bruno,

CA; RDT&ELO San Bruno, CA NAVFACENGCOM CONTRACTS Eng Div dir. Southwest Pac, Manila, PI; OICC, Southwest Pac, Manila. PI;

OICC/ROICC, Balboa Panama Canal; ROICC Code 495 Portsmouth VA; ROICC, NAS, Corpus Christi, TX; ROICC. Yap

NAVOCEANO Library Bay St. Louis. MS NAVOCEANSYSCEN Code 09 (Talkington). San Diego, CA; Code 4473 Bayside Library, San Diego, CA;

Code 4473B (Tech Lib) San Diego, CA; Code 5204 (.1. Stachiw), San Diego. CA; Code 5214 (H. Wheeler), San Diego CA; Code 5221 (R.Jones) San Diego Ca; Code 5322 (Bachman) San Diego, CA; Hawaii Lab (R Yumori) Kailua. HI; Hi Lab Tech Lib Kailua HI

NAVPGSCOL C. Morers Monterey CA; Code 61WL (O. Wilson) Monterey CA; E. Thornton, Monterey CA '.";N NAVPHIBASE CO, ACB 2 Norfolk. VA; COMNAVBEACHGRU TWO Norfolk VA; Code S3T, Norfolk VA; ''.'* Harbor Clearance Unit Two, Little Creek, VA; SCE Coronado, SD.CA *'_.-'; NAVREGMEDCEN SCE; SCE. Guam ^ NAVSCOLCECOFF C35 Port Hueneme, CA $*% NAVSCSOL PWO, Athens GA "-"- NAVSEASYSCOM Code OOC-D, Washington, DC; Code PMS 395 A 3. Washington, DC; Code PMS 395 A2.

Washington, DC; Code PMS 396.3311 (Rekas). Wash.. DC; Code SEA OOC Washington. DC; PMS-395 Al, Washington, DC; PMS395-A3. Washington. DC

NAVSECGRUACT PWO. Adak AK NAVSHIPREPFAC Library, Guam; SCE Subic Bay NAVSHIPYD Bremerton. WA (Carr Inlet Acoustic Range); Code 202.4, Long Beach CA; Cod.- 280, Mare Is.,

Vallejo, CA; Code 280.28 (Goodwin), Vallejo. CA; Code 440 Portsmouth NH; Code 440, Puget Sound, Bremerton WA; Tech Library, Vallejo. CA

NAVSTA CO Roosevelt Roads PR. Puerto Rico; Dir Engr Div. PWD, Mayport FL; PWD (LTJG.P.M. Motolenich). Puerto Rico; PWO. Keflavik Iceland; PWO. Mayport FL; SCE, Guam; SCE, Subic Bay. R.P.; Security Offr. San Francisco, CA

NAVTECHTRACEN SCE, Pensacola FL NAVWPNSTA Code 092. Colts Neck NJ NAVWPNSTA PW Office Yorktown. VA NAVWPNSTA PWD "- Maint. Control Div.. Concord. CA; PWD - Supr Gen Engr. Seal Beach. CA; PWO,

Charleston, SC; PWO. Seal Beach CA NAVWPNSUPPCEN Code 09 Crane IN NCBC Code 10 Davisville, RI; Code 15, Port Hueneme CA; Code 155. Port Hueneme CA; Code 156, Port

Hueneme, CA; Library, Davisville, RI; Technical Library. Gulfport, MS NMCB FIVE, Operations Depi NOAA (Mr. Joseph Vadus) Roekville, MD; Library Roekville. MD NORDA Code 410 Bay St. Louis. MS; Code 440 (Ocean Rsch Off) Bay St. Louis MS; Code 500. (Ocean Prog

Off-Ferer) Bay St. Louis. MS NRL Code 5800 Washington. DC; Code 5843 (F. Rosenthal) Washington. DC; Code 8441 (R.A. Skop),

Washington DC NROTC J.W. Stephenson. UC, Berkeley. CA NSD SCE. Subic Bay. R.P. NUCLEAR REGULATORY COMMISSION T.C. Johnson. Washington. DC NUSC DEI Code 131 New London, Cl; Code EA123 (R.S Munn). New London Cl; Code TA131 (G. De la

Cruz), New London CT ONR Central Regional Office, Boston. MA; Code 481, Bay St. Louis. MS; Code 485 (Silva) Arlington. VA;

Code 700F Ailington VA PI11BCB 1 P&E, San Diego, CA; I, CO San Diego. CA PM'IC Code 3144, (E. Good) Point Mugu. CA; Code 3331 (S. Opatowslu) Point Mugu. CA; EOD Mobile

Unit. Point Mugu. CA PWC CO, (Code 10). Oakland. CA; Code 10, Great Lakes. 1L; Code 120, Oakland CA; Code 128. Guam;

Code 154 (Library). Great Lakes. IL; Code 2:00. Great Lakes IL; Code 4(H). Great Lakes. IL; Code 400. Pearl Harbor, HI; Code 400. San Diego. CA; Code 420. Great Lakes. II ; Code 420. Oakland. CA; Code 424. Norfolk, VA; Code 500 Norfolk, VA; Code 700, San Diego, CA; Library (ode I20C. San Diego. CA;

70

Library, Guam; Library. Norfolk, VA; Library, Pearl Harbor, HI; Library. Pensacola. FL; Library. Subic Bay, R.P.; Library, Yokosuka JA

UCT ONE OIC. Norfolk, VA UCT TWO OIC. Port Hueneme CA US DEPT OF INTERIOR Bur of Land Mgmnt Code 583, Washington DC US GEOLOGICAL SURVEY Off. Marine Geology, Piteleki, Reston VA US NAVAL FORCES Korea (ENJ-P&O) USCG (G-MP-3/USP/82) Washington Dc US GEOLOGICAL SURVEY (Chas E. Smith) Minerals Mgmt Serv, Reston. VA USCG G-EOE-4 (T Dowd), Washington, DC; Library Hqs Washington. DC USCG R&D CENTER CO Groton. CT; D. Motherway, Groton CT; Library New London. CT USDA Ext Service (T. Maher) Washington. DC; Forest Service. San Dimas, CA USNA ENGRNG Div. PWD. Annapolis MD; USNA/SYS ENG DEPT ANNAPOLIS MD WATER & POWER RESOURCES SERVICE (Smoak) Denver, CO NUSC DET Library. Newport, RI

71

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INSTRUCTIONS

The Naval Civil Engineering Laboratory has revised its primary distribution lists. The bottom of the mailing label has several numbers listed. These numbers correspond to numbers assigned to the list of Subject Categories. Numbers on the label corresponding to those on the list indicate the subject category and type of documents you are presently receiving. If > o i are satisfied, throw this card away (or file it for later reference).

If you want to change what you are presently receiving:

• Delete - mark off number on bottom of label.

• Add - circle number on list.

• Remove mv name from all vour lists - cheek box on list.

• Change my address - line out incorrect line and write in correction (ATTACH MAILING LABEL).

• Number of copies should be entered after the title of the subject categories you select.

Fold on line below and drop in the mail.

Note: Numbers on label but not listed on questionnaire are for NCELuse only, please ignore them.

Fold on line and staple.

DEPARTMENT OF THE NAVY

NAVAL CIVIL ENGINEERING LABORATORY PORT HUENEME, CALIFORNIA 93043

OFFICIAL BUSINESS PENALTY FON PRIVATE USE. »300

1 IND-NCEL-270O/4 (REV. 12-73)

0SS0-LI-L70-0044

POSTAGE AND FEES PAID DEPARTMENT OF THE NAVY

DOD-31S

Commanding Officer

Code L.14 Naval Civil Engineering Laboratory Port Hueneme, California 93043

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*9*4

DISTRIBUTION QUESTIONNAIRE

The Naval Civil Engineering Laboratory is revising its primary distribution lists.

SUBJECT CATEGORIES

1 SHORE FACILITIES 2 Construction methods and materials {including corrosion

control, coatings) 3 Waterfront structures (maintenance/deterioration control) 4 Utilities (including power conditioning) 5 Explosives safety 6 Construction equipment and machinery 7 Fire prevention and control . 8 Antenna technology 9 Structural analysis and design (including numerical and

computer techniques) 10 Protective construction (including hardened shelters,

shock and vibration studies) 11 Soil/rock mechanics 13 BEQ 14 Airfields and pavements 15 ADVANCED BASE AND AMPHIBIOUS FACILITIES 16 Base facilities (including shelters, power generation, water supplies; 17 Expedient roads/airfields/bridges 18 Amphibious operations (including breakwaters, wave forces) 19 Over-the-Beach operations (including containerization,

materiel transfer, lighterage and cranps) 20 POL storage, transfer and distribution 24 POLAR ENGINEERING 24 Same as Advanced Base and Amphibious Facilities,

except limited to cold-region environments

TYPES OF DOCUMENTS

85 Techdata Sheets 86 Technical Reports and Technical Notes

83 Table of Contents & Index to TDS

28 ENERGY/POWER GENERATION 29 Thermal conservation (thermal engineering of buildings, HVAC

systems, energy loss measurement, power generation) 30 Controls and electrical conservation (electrical systems,

energy monitoring and control systems) 31 Fuel flexibility (liquid fuels, coal utilization, energy

from solid waste) 32 Alternate energy source (geothermal power, photovoltaic

power systems, solar systems, wind systems, energy storage systems)

33 Site data and systems integration (energy resource data, energy consumption data, integrating energy systems)

34 ENVIRONMENTAL PROTECTION 35 Solid waste management 36 Hazardous/toxic materials management 37 Wastewatfir management and sanitary engineering 38 Oil pollution removal and recovery 39 Air pollution 40 Noise abatement 44 OCEAN ENGINEERING 45 Seafloor soils and foundations 46 Seafloor construction systems and operations (including

diver and manipulator tools) 47 Undersea structures and materials 48 Anchors and moorings 49 Undersea power systems, electromechanical cables,

and connectors 50 Pressure vessel facilities 51 Physical environment (including site surveying) 52 Ocean-based concrete structures 53 Hyperbanc chambers

54 Undersea cable dynamics

82 NCEL Guide 8< Updates

91 Physical Security

r; Nonc- rcmove my name

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SUPPLEMENTARY

v

INFORMATION

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DEPARTMENT OF THE NAVY NAVAL CIVIL ENGINEERING LABORATORY

PORT HUENEME, CA 93043 IN REPLY REFER TO

L08/PDT/jw 42-040 Serial 450 19 Mar 84

From: Commanding Officer To: Distribution

Subj: Errata Sheet for Technical Note TN-1688, "Design Guide for Drag Embedment Anchors," by R. Taylor.

1. Please replace page 39 with attached page 39.

P. D. TRIEM By direction

hr.

D/L

Figure 7.2 Predicted normalized fluke tip penetration versus normalized drag distance.

1000 c

.a

40 oO 80 100

ANCHOR AIR HEIGHT MA (KIPS)

Figure 7.3 Anchor holding capacity factor, NcfBL, versus anchor air weight, WA, based on anchor designs available in June 1982.

39